Current vehicle airbag systems include an inflatable airbag that is positioned in an airbag housing. When inside the housing, a cover is situated over the airbag. The cover may be, for example, an airbag deployment door, seat trim, substrate, or closeout. These covers, which are intended to be permanent and irreversible following airbag deployment, are either integral with the housing or are attached via an attachment mechanism. Exemplary attachment mechanisms may include irreversible stitching, rivets, or threaded fasteners. The portion of the surface acting as the cover is typically demarked by a weakened region around all or a portion of its perimeter, which is not typically visible to the end consumer. The weakened region is designed to fail under airbag loading during deployment, creating an opening through which the airbag may deploy.
The fracture forces necessary to open an airbag cover may experience some level of variation from part to part due to manufacturing and part tolerance differences. The inherent variability of the separation and release of the airbag cover causes variation in both the timing and the manner in which the airbag deploys through the cover. Such variability requires the airbag system to have an inflator with a higher power than may otherwise be necessary to provide accurate and predictable deployment.
As such, it is desirable to control the deployment of an airbag past the airbag cover, reduce the cover fracture forces, and, thus, minimize the required power of the airbag inflator.